There are a number of in situ techniques for recovering hydrocarbons, such as heavy oil and bitumen, from subsurface reservoirs. Thermal in situ recovery techniques often involve the injection of a heating fluid, such as steam, in order to heat and thereby reduce the viscosity of the hydrocarbons to facilitate recovery.
One technique, called Steam-Assisted Gravity Drainage (SAGD), has become a widespread process for recovering heavy oil and bitumen particularly in the oil sands of northern Alberta. The SAGD process involves well pairs, each pair having two horizontal wells drilled in the reservoir and aligned in spaced relation one on top of the other. The upper horizontal well is a steam injection well and the lower horizontal well is a production well.
Numerous wells or well pairs are usually provided in groups extending from central pads for hundreds of meters often in parallel relation to one another in order to recover hydrocarbons from a reservoir.
For such thermal in situ recovery operations utilizing steam injection, a steam chamber is formed and tends to grow upward and outward within the reservoir, heating the bitumen or heavy hydrocarbons sufficiently to reduce the viscosity and allow the hydrocarbons and condensed water to flow downward toward the production well. However, heating the reservoir and controlling the flow of hydrocarbon-containing fluids along the production well present a number of challenges.
For example, inflow distribution can be biased toward one or more sections of the production well, which can lead to poor temperature conformance, reduced production rates, and uneven drawdown distribution along the production well. Additionally, avoidance of steam breakthrough by maintaining an optimal steam-fluid interface between the well pair involves a proper control of the amount of fluid being drawn into the production well. In some instances, distributed flow control devices have been provided in well completion designs, in an attempt to ensure that the steam chamber extends as close as possible to the production well but not so close as to cause steam breakthrough.
Accordingly, various challenges still exist in the field of thermal in situ hydrocarbon recovery, inflow distribution and steam breakthrough control, and well conformance management.